What would "proper regulation" be, and why isn't a registration and review system for hosts such?
(If it turns out it was the city's fault that Airbnb erroneously thought the registration was invalid, that'd clearly be an implementation failure, I agree, but still leaves open the question why Airbnb only reacted so late)
If only there was a way to make tourists and hosts pay for the inconvenience and externalities they cause, and put that revenue to the benefit of everyone in the city. I know, let's call it a tax.
As opposed to a rigid system of "designated uses" for private properties that prevents economic transactions depending on how much they inconvenience upper class and politically connected residents and competing hospitality interests.
If I'm living in a building and it becomes intolerable because of noisy transient visitors on a regular basis, a tax that goes to the city does me no good whatsoever.
If you are in a condo, your homeowners association should have rules about making noise, and the owners of the airbnb should be forced to take responsibility. If an apartment complex, your landlord should deal with it.
Or, and here's an idea, we can enact sane regulations like licensing requirements to prevent the negative externalities from happening in the first place.
Enacting sane regulation that does what it is intended to do and has no or few side effects is more difficult when you try to regulate each individual action some one could take that may have negative externalities, rather than regulating the production of the negative externalities.
Edit to add:
And by regulating local externalities at the local building level rather than the city level, you are more likely to have better regulations in regards to residents and owners wishes.
It happened in the last flat I rented. In the end we had to threat the owner with violence and property destruction, so finally he rented it long term to some guys.
It's sad to get to this point but nobody was going to do anything and I was no way willing to deal with that situation. One tourist even pissed in the elevator.
(If it turns out it was the city's fault that Airbnb erroneously thought the registration was invalid, that'd clearly be an implementation failure, I agree, but still leaves open the question why Airbnb only reacted so late)